And now a note as to why a VNC Server for OS X would be a good thing, even if we get OS X native forwarding.
1) VNC is a very thin-client protocol. That is, a client is small, relatively easy to write, does very little, and requires very little from the processor or RAM. This leads to huge multiplatform capabilities. I\'ve seen palmtop devices running X windows remotely over VNC. I seriously doubt that such a device could handle an Exceed or xTools type solution, even if there was a developer intrepid enough to try to make one.
The genius of VNC is that it does not send commands native to any particular environment across the network. Instead, the VNC server pre-renders the screen (*NIX) or copies the pre-rendered screen (Mac, Win) and sends pixels over a network, thus assuming absolutely NOTHING about the nature of the client. (This is also the root of the speed problem, because pushing pixels is slow. But, it is really easy on the client, which X11-stype forwarding is emphatically not, which is why xTools and Exceed cost a lot of money.)
I have yet to be convinced that the fact that Quartz uses PDF commands means that remote clients will be able to be anywhere near as thin as even ghostview. Rendering static PDF files is emphatically not the same as being able to render streaming PDF commands in real time, if indeed this is what OS X forwarding will be. (Strobes last post makes me think that this will indeed be the case. Comparisons to NeXT are very instructive -- thanks!)
I tend to think that insofar as the Quartz layer itself is far more complicated than ghostview, any remote client recieving windowing commands intended for Quartz to render will need significantly more than the ghostview codebase can offer.
If OS X forwarding follows the X11 model, the remote server will need the full capabilities of a local display server in order to properly render the screen. And as nice as Ghostivew and other PDF viewers are, they are not Quartz, and I really dont think that making them quote Quartz compatible would be a trivial thing. Just cranking up the render speed so such a thing would be real-time usable could prove very difficult.
In fact, if there is or will be an API for a VNC server to tap into the Quartz-generated pixel stream (see previous post) I would bet that porting a VNC server to OS X would be far, far easier than hacking up Ghostview or something to be a full-fledged OS X client on even one platform!
Of course, I might be wrong. Did anyone ever make any postscript interpreters into remote clients for NeXT? If this was easily done, than I must concede this point to Strobe.
2) VNC is here already. There is a large base of tested, running clients on every OS imaginable . More OSs have VNC ports than have Ghostview ports. Even if a remote client of X can be as thin as VNC and can build off of Ghostview, it will take a long time for the ports to reach the penetrance that VNC has (if ever).
[Strobe, when I said Quartz clients of onther systems would be \"slow in coming\" I meant porting speed, not render or network speed. Which, you are right, PDF forwarding would beat VNC in any day.]
Sorry for the long post. My point here is that I think that both X11 or NeXT-style forwarding and VNC are complimentary solutions, each useful in areas where the other is not. (X11 for speed, VNC for ease of client porting and for running clients on nontraditional platforms -- like the Java VNC client that allows me to operate my system from within a web page.)